Method of refinishing engine cylinders



June 27, 1933. o. A. DAHLBERG METHOD OF REFINISHING ENGINE CYLINDERSFiled June 1o, 1932 Il l III IIHIIII Patented June 27, 1.933

unirse se'rariisA PATENT omer:

OSCAR A. DAHLBERG, or Miivivniiroiiis, Miiviviisofre, Assieivon ToJOSEPH sUivNEN,

or innxwoon,v MISSOURI METHOD OF lCElFIN'SI-IING ENGINE CYLINDERS l'Application mea June 1o,

My invention has relation to improvementsin methods of refinishingengine cylinders and devices therefor and it consists in the novelfeatures and principles of con-v face for the first grinding, or roughgrindingI operation, followed by one or more fine grinding operations inwhich abrasive elements having successively finer grinding surfaces areused, after which a burnishing operation is employed. This'latteroperation consists' in scouring or burnishing the cylinder wall by meansof a burnishing brush or a set of brushes mounted in the same or similarholder which was used in the abrading or grinding operations.

rIhe invention includes the burnishing-deoperation on the cylinder isperformed.` Grinding stones, or hones, operate, asis Well known, byabrasion, and when a: cylinder is reconditioned by grinding,s'harpabrasion scores remain `on the wall of the cylinder, even though arelatively fine stone'is used for the final grinding operation. If thecylinder is vtrue these scores are tolerated 'because they are uniformlydistributed over ence of the abrasion marks prevents -a newly groundcylinder from functioning at its maximum efficiency until after it hasbeen operated a certain length of time, or worn in. Of course, duringthis wearing in, or smoothing operation, excessive wear comes on thepiston rings so that they are seriously damaged by the time the`cylinder wall has been worn smooth. n

My invention obviates to a large extent the necessity of wearing in thecylinder by use, as it provides means for wearing off the sharp edges ofthe abrasion marks, and thus burnishing the cylinder wall as a final, orfinishing step, in the reconditioning of worn f; vice or brush Vwithwhich the finer finishingthe entirecylinder wall. However, the pres1932.- Serial No. 616,411.

and out of round cylinders. After reground cylinders have been`burnished lwith my improved device they are smooth, and require verylittle wearing in. Obviously, the piston rings are thus subjected to nomore than normal wear when first operated in a reground cylinder andwillffunction efficiently for a longer time than otherwise.

`It isa further object of the invention to provide a burnishing brushthat may be substituted'for the abrasive element in a Sum nen7 cylindergrinder of the type shown in the co-pending application of JosephSunnen, Serial No. 233,788, filed November '17, 1927, so that a singleholder will sufhce for performing `both the grinding and burnishingoperations. Further and other advantages will be better apparent from adetailed description of the invention in connection with theaccompanying drawing, in which: l

Figure l is a side elevation of my improved burnishing devicev withparts of the brush holder and parts of one of the brushes broken away;Fig. 2isk aphorizontal. cross-section of the device taken on the vzigzaglinev2-2 of Fig.v l; Fig. `3 is a.l longitudinal section through thebrush taken on the line 3+?) of Fig. l; Fig. ZLisa greatly enlargedcross-seotion through a fragment of ycylinder `wall showing theabrasion, marks on the inner surface thereof before the cylinder wallhas been burnished by my improved device; and Fig. 5 is anlenlargedcross-'section through the same cylinder wall portion after the saidcylinder wall has been burnished. c

Referring to the drawing, l represents the tool holder of a- Sunnencylinder grinder of the type described in theabo've referred to patentapplication, said holder being suspended by yoke 2 and collar 3 from ashaft 4. rlhe collar 3 ispivotally connected to the holder l by means ofstuds 5, 5 and the'yokel 2 is pivotally connected to the collar by meansof studs 6, 6 so thata universal joint connection is V.formed betweenthe shaft 4f and 90 the holder l. The holder l is provided with alongitudinally disposed axial bore 7 withinv which is housed a pinionshaft 8 rotatable by means of the adjusting head 9 for the purpose ofextending and retracting the brushes ffl 10, 10. The construction andthe operation of the tool holder, comprising the parts just described,is substantially the same as that of the holder of the honing devicedescribed in detail in the aforesaid patent application and will not befurther described herein except insofar as necessary to explain theoperation of the burnishing elements, or brushes io, 1o.

Each of the brushes comprises a body portion 11 from the back of whichJtoothed pins or rack bars 12, 12 project, said rack bars supporting thebrush in the holder 1 by virtue of spaced openings 13, 13 (there being apair of such openings for each brush) in which the rack bars aremounted. It will be observed that openings 13 intersect the bore 7 andthe teeth of pinion 8 project into each of said openings 13 so that theywill mesh with the teeth t of each rack bar 12, whereby the rack barsare simultaneously moved inwardly or outwardly with the rotation of thepinion 8 so as to effect uniform adjustment of the brushes to lit thecylinder C within which they are being operated. The mounting of thebrushes and the method of adjusting the same is the same as thatemployed when abrasive elements are used, as described in theapplication referred to, and in practice the brushes are constructed sothat they will be interchangeable with the abrasive elements. Thus amechanic need have but a single holder with his set of grinding tools,or abrasive elements, and burnishing elements. Afterhe has performed theroughgrinding operation upon a cylinder, followed up by the smoothgrinding operation he-replaces the grinding elements with the burnishingelements, or brushes 10, whereupon the burnishing operation is performedin exactly the same manner that the grinding operations were performed.

The specific manner of constructing the brush is immaterial, althoughl lillustrate'a construction that is durable and otherwise satisfactory.The brush body 11 is provided with side walls 14, 14 bent inwardly so asto form a channel in which a block 15 is inserted, said block being heldsecurely therein by means of screws 16, 16 passed through threadedopenings 17, 17 in the brush body 11 and into said block 15. The block15 carries wire bristle tufts 18, said tufts being held therein in anysuitable manner and being sufiic-iently close together so that the endsof the bristles will merge together so as fo form a compact burnishingsurface.

In refinishing worn engine cylinders the tool holder 1 is first equippedwith abrading elements instead of burnishing elements, said abradingelements having a rough finish so as to reduce the cylinder wall rapidlyto a correct shape, after which, as heretofore pointed out, these roughgrinding elements are replaced by a grinder having a less severeabrading effect so as to smooth off the roughness left by the roughgrinder. However, as long as an abrading element is used on the cylinderwall there will be abrasive scores with sharp edges which would have tobe smoothed out by the operation of the engine unless some other meansare used to perform this smoothing operation. I have discovered thatthese abrasion scores may be reduced and smooth-ed by my improveddevice. It is apparent that when four brushes are mounted in a holder(as shown in F ig. 2) and are rapidly rotated over the inner surface ofcylinder C they will not only scrub the wall of said cylinder to cleanit of all loose adhering particles of grindings, but the stiffl bristleswill also remove all burrs that remain from the grinding operationV andround 0H the sharp abrasive marks, such as shown in Fig. 4, so that suchabrasive marks will more or less assume the contour shown in Figure 5.r1`hat these sharp abrasive marks are actually worn off is apparent by amicroscopic inspection of the cylinder surface. The smoothness of thecylinder wall after burnishing the same with my improved burnishingdevice is also apparent to the touch when said cylinder wall iscarefully felt both before the finishing operation and after thefinishing operation.

Having described my invention, I claim: 1. rllhe method of refinishingengine cylinders which comprises performing a grinding operation on thecylinder wall with an abrasive element, performing a second grindingoperation with an abrasive element of greater lineness than the first,and finally burnishing said wall with a suitable brush.

2. The method of finishing engine cylinders which comprises rapidlyrotating a stiff wire brush in contact with the cylinder wall to removeloose adhering articles there-` from, moving said brush into moreintimate contact with the wall and continuing said rotation'to burnishsaid wall.

3. The method of refinishing engine cylinders which comprises performinga grinding operation on the cylinder wall with an abrasive element andthereafter moving a wire brush over said cylinder wall with sufficientpressure to burnish the same.v

4. The method of refinishing engine cylinders which comprises performinga grinding operation on a cylinder wall with an abrasive element, thenrapidly rotating a stiff wire brush in contact with the cylinder wall toremove loose adhering particles, and finally moving said brush into moreintimate contact with the wall and continuing said rotation to burnishsaid wall.

In testimony whereof 1 hereunto afiiX my signature.

OSCAR A. DAHLBERG.

lli)

